diff --git a/firmware/film-scanner-fw/.cargo/config.toml b/firmware/film-scanner-fw/.cargo/config.toml
index dc027bf..774199e 100644
--- a/firmware/film-scanner-fw/.cargo/config.toml
+++ b/firmware/film-scanner-fw/.cargo/config.toml
@@ -20,7 +20,7 @@ rustflags = [
 ]
 
 [build]
-target = "thumbv6m-none-eabi"
+target = "thumbv7em-none-eabihf"
 
 [env]
-DEFMT_LOG = "debug"
\ No newline at end of file
+DEFMT_LOG = "debug"
diff --git a/firmware/jerk_control/src/bin/sqrt_test.rs b/firmware/jerk_control/src/bin/sqrt_test.rs
new file mode 100644
index 0000000..a4f791a
--- /dev/null
+++ b/firmware/jerk_control/src/bin/sqrt_test.rs
@@ -0,0 +1,36 @@
+fn ulp(f: f32) -> f32 {
+    f32::from_bits((f.to_bits() & 0x7f80_0000) - 0x0b80_0000)
+}
+
+fn fn_err(actual: f32, calc: f32) -> f32 {
+    (calc - actual).abs() / actual
+}
+
+
+fn test_all(fname: &str, actual: fn(f32) -> f32, calc: fn(f32) -> f32) {
+    let mut max_err = 0f32;
+    let mut max_err_value = 0f32;
+    for i in (0x00c0_0000..0x0f7f_ffffu32).map(f32::from_bits) {
+        // range of normalized floats...
+        let err = fn_err(actual(i), calc(i));
+        if err > max_err {
+            max_err = err;
+            max_err_value = i;
+	    }
+	}
+
+    let max_err_pct = max_err * 100f32;
+    println!("{}: {}% @ {}", fname, max_err_pct, max_err_value);
+    println!(
+        "Value:      0x{:08x}\n
+        Calculated: 0x{:08x}\n
+        Actual:     0x{:08x}",
+        max_err_value.to_bits(),
+        calc(max_err_value).to_bits(), actual(max_err_value).to_bits())
+}
+
+
+fn main() {
+    // test_all("sqrt", f32::sqrt, jerk_control::math_ext::Roots::sqrt);
+    test_all("cbrt", f32::cbrt, jerk_control::math_ext::Roots::cbrt);
+}
\ No newline at end of file
diff --git a/firmware/jerk_control/src/lib.rs b/firmware/jerk_control/src/lib.rs
index 52987a0..d2f90d3 100644
--- a/firmware/jerk_control/src/lib.rs
+++ b/firmware/jerk_control/src/lib.rs
@@ -1,2 +1,6 @@
+// #![no_std]
+
 pub mod planner;
-pub mod executor;
\ No newline at end of file
+pub mod executor;
+
+pub mod math_ext;
diff --git a/firmware/jerk_control/src/planner.rs b/firmware/jerk_control/src/planner.rs
index 6da8f9d..f413e9c 100644
--- a/firmware/jerk_control/src/planner.rs
+++ b/firmware/jerk_control/src/planner.rs
@@ -4,6 +4,7 @@
 //! All of their derivations can be found in the motion-control.ipynb file.
 
 use core::num::Wrapping;
+use core::option::Option;
 
 pub struct Config {
     /// Max jerk, in mm/s^3
@@ -162,7 +163,7 @@ impl Planner {
             .clamp(0.0, (1u32 << 31) as f32);
         let step_size = config.step_size * 6. * tick_rate * tick_rate * tick_rate / config.j_max;
         if step_size > (u32::MAX / 2) as f32 {
-            eprintln!("Failed to configure planner: stepsize = {}", step_size);
+            //eprintln!("Failed to configure planner: stepsize = {}", step_size);
             return false;
         }
         self.a_max = a_max as u32;
@@ -212,7 +213,7 @@ impl Planner {
         let tv = (dx - ramp_dx) * 2 / s4v as u64;
         let tv = ((tv + 1) / 2) as u32;
 
-        eprintln!("ta={ta}, tj={tj}, tv={tv}");
+        //eprintln!("ta={ta}, tj={tj}, tv={tv}");
         let j_real = dir * 6;
         let mut segments = [Segment::default(); 8];
         let seg_params = [
diff --git a/firmware/motion-tester/Cargo.toml b/firmware/motion-tester/Cargo.toml
index 1e48dda..0f942f8 100644
--- a/firmware/motion-tester/Cargo.toml
+++ b/firmware/motion-tester/Cargo.toml
@@ -7,4 +7,6 @@ edition = "2021"
 
 [dependencies]
 jerk_control = { path = "../jerk_control" }
-structopt = { version = "0.3.26" }
\ No newline at end of file
+# structopt = { version = "0.3.26" }
+
+rayon = "1.5.2"
\ No newline at end of file
diff --git a/firmware/motion-tester/src/bin/math_test.rs b/firmware/motion-tester/src/bin/math_test.rs
new file mode 100644
index 0000000..913f080
--- /dev/null
+++ b/firmware/motion-tester/src/bin/math_test.rs
@@ -0,0 +1,47 @@
+use rayon::prelude::*;
+
+fn ulp(f: f32) -> f32 {
+    f32::from_bits((f.to_bits() & 0x7f80_0000) - 0x0b80_0000)
+}
+
+fn fn_err(actual: f32, calc: f32) -> f32 {
+    (calc - actual).abs() / actual
+}
+
+
+fn test_all(fname: &str, actual: fn(f32) -> f32, calc: fn(f32) -> f32) {
+    let mut max_err = 0f32;
+    let mut max_err_value = 0f32;
+    (0x01..=0xfe).into_par_iter()
+        .map(|exp| {
+            (0x0..=0x7f_ffff).map(|mant| f32::from_bits((exp << 23) + mant))
+                .max_by_key(|value| fn_err(actual(*value), calc(*value)).to_bits())
+                .unwrap()
+        })
+        .map(|value| (value,fn_err(actual(value), calc(value))))
+        .collect::<Vec<_>>();
+
+    for i in (0x0400_0000..0x0f7f_ffffu32).map(f32::from_bits) {
+        // range of normalized floats...
+        let err = fn_err(actual(i), calc(i));
+        if err > max_err {
+            max_err = err;
+            max_err_value = i;
+        }
+    }
+
+    let max_err_pct = max_err * 100f32;
+    println!("{}: {}% @ {}", fname, max_err_pct, max_err_value);
+    println!(
+        "Value:      0x{:08x}\n
+        Calculated: 0x{:08x}\n
+        Actual:     0x{:08x}",
+        max_err_value.to_bits(),
+        calc(max_err_value).to_bits(), actual(max_err_value).to_bits())
+}
+
+
+fn main() {
+    // test_all("sqrt", f32::sqrt, jerk_control::math_ext::Roots::sqrt);
+    test_all("cbrt", f32::cbrt, jerk_control::math_ext::Roots::cbrt);
+}
\ No newline at end of file